Immunotherapy before surgery may reduce colon cancer recurrence

• Initial trial results suggest that a short course of immunotherapy given before surgery in stage 2 to 3 colorectal cancer patients resulted in no cancer recurrences after nearly 3 years of follow-up.
• In the trial, 59% of patients had no detectable cancer after treatment, and even those with small amounts remaining showed no disease progression.
• The approach appears especially effective for patients with MMR-deficient/MSI-high colon cancer, a subgroup that accounts for about 10 to 15% of cases in the United Kingdom.
• Monitoring tumor DNA in the blood helped predict which patients responded best, suggesting a way to personalize treatment and potentially reduce or avoid chemotherapy.

Colorectal cancer, describing cancer that starts in the colon or the rectum, is the third most common cancer worldwide, and the second leading cause of cancer-related deaths worldwide.

Surgery is the most common treatment for colon cancer. Often, people may receive chemotherapy prior to the surgery, known as neoadjuvant therapy, to help shrink the tumor, make it easier to remove, and help with bowel control.

However, while neoadjuvant chemotherapy can be an effective option, it does not work equally well for everyone.

A certain genetic profile, known as MMR-deficient/MSI-high colon cancer, accounts for roughly 15% of those with stage 2 to 3 colon cancer.

Research suggests this type of colon cancer is less responsive to chemotherapy, and growing evidence indicates that immunotherapy may produce longer-lasting responses and better survival than standard chemotherapy for many patients.

Now, a clinical trial led by researchers at University College London (UCL), in the United Kingdom, suggests that a short course of immunotherapy given before surgery could significantly improve outcomes for those with MMR-deficient/MSI-high colon cancer.

The findings, presented at the American Association for Cancer Research Annual Meeting 2026, suggest that this approach may challenge the current standard of care, and potentially reduce the need for chemotherapy in certain patients.